Well, I haven't actually read this specific fanfiction. But generally, it might involve Harry Potter's adventure to discover the Sword of Zen Aku. Maybe he faces a series of challenges and uses his magic skills to overcome them. It could also introduce new characters or settings related to the sword.
Well, if Harry Potter finds the Mask of Zen - Aku, it could lead to a lot of chaos. Maybe the magic of the mask would interact in strange ways with Harry's own magic. He might struggle to control the power of the mask and find himself in situations where he has to make difficult choices between using the mask's power for good or being corrupted by it.
One idea could be that the Sword of Zen Aku is hidden in an ancient and forgotten chamber in Hogwarts. Harry discovers an old map or prophecy that leads him to it. Another idea is that the sword has been stolen by a dark wizard and Harry has to track it down. Maybe the sword has the power to control certain magical elements, like the ability to stop a dark curse that's spreading across the wizarding world.
The mask could potentially strain Harry's relationships. His friends might be worried about him using the mask and getting corrupted. For instance, Hermione could be very cautious and try to persuade Harry to get rid of the mask. This might cause some friction between them as Harry might be more curious about the mask's power.
I'm not sure who Aku specifically is. Aku could be a person with a great imagination who tells all kinds of stories, like adventure stories, fairy tales or even true - life stories.
Funny Zen stories usually carry a message of acceptance. They show that in Zen, all things are as they are. For instance, a story could be about a clumsy novice monk who keeps dropping things. Instead of scolding him, the master says it's all part of the learning process, teaching us to accept our own imperfections and those of others.
It could be someone from the Naruto universe who doesn't like Naruto's newfound fascination with Aku. For example, Danzo might see Naruto's interest in Aku as a threat to the stability of the village and try to stop Naruto from further exploring Aku - related things. So, Danzo could be the main antagonist in this case.
The character of Aku could be developed in a 'pregnant Aku in Samurai Jack fanfiction' by exploring how he interacts with the world around him differently. He may become more reclusive as he doesn't want others to see his 'weak' state. Or he could become more aggressive in trying to protect his pregnancy, which would be a new aspect of his character. Also, his relationship with his own power might change. Maybe he has to find new ways to use his magic that don't harm the unborn, which would force him to grow and adapt in ways he hasn't before.
One idea could be a crossover where Aku accidentally opens a portal to the Naruto universe. Naruto, being the curious and brave ninja he is, decides to explore Aku's world. They could start off as enemies, but gradually come to understand each other's motives and end up teaming up against a greater evil that threatens both of their worlds.